Field of the Invention
The invention relates to a semiconductor device and a method of operating the same, and more particularly relates to a memory device and a method of operating the same.
Description of Related Art
Generally, a non-volatile memory can repeatedly perform operations of data writing, reading, and erasing and is advantageous in that the data stored therein does not disappear even when the power supply is shut down. For this reason, the non-volatile memory has been widely used as the memory device for personal computers and electronic products for maintaining normal operation when power is on.
Nevertheless, as the integrity of semiconductor devices increases, the size of each component in the memory device continues to decrease. For example, when the size of the memory cell of an NAND flash memory is reduced, the critical dimension of the sub-30 nm floating gate is also limited. In order to achieve high density and high performance, fabrication of semiconductor devices has evolved into stacking upward in the vertical direction, such that the wafer area can be used more efficiently. Therefore, semiconductor structures with a high aspect ratio are common in small-sized devices.
However, performing lithographic and etching processes for fabricating small-sized devices with a high aspect ratio is a challenge. For instance, one conductor layer near the substrate surface may be connected with the adjacent conductor layer due to incomplete etching. It may cause problems, such as slow programming, charge loss, and charge gain, when voltages are applied to the devices in the subsequent process. Hence, how to overcome the aforementioned electrical problems, caused by incomplete etching, under the limitation of the etching process is an important issue in this field.